<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div {
            width: 100px;
            height: 100px;
        }
    </style>
</head>

<body>
    <div>

    </div>

    <script>
        const a = document.querySelector('div');
        a.style.backgroundColor = color()
        function color() {
            let r = Math.floor(Math.random() * 256)
            let g = Math.floor(Math.random() * 256)
            let b = Math.floor(Math.random() * 256)
            return `rgb(${r},${g},${b})`
        }
        const obj = { name: '张三' }
        obj.name = '李四'
        const box = document.querySelector('.box')
        box.innerHTML = '<strong>hello</strong>'

    </script>
</body>

</html>